1. Field of Invention
The present invention relates to a track for an endless drive track system. More particularly, the present invention relates to an endless drive track having an improved drive lug configuration for use with a tracked vehicle such as a tractor, bulldozer or tank.
2. Description of Related Art
Conventional endless drive track systems are used with tracked vehicles such as tractors, bulldozers, tanks or the like, as shown in U.S. Pat. No. Re. 33,324, incorporated herein by reference. As shown in FIG. 1 herein, a vehicle 1 includes an endless drive track system 2 with an endless track 3, a drive system, e.g., a planetary drive system 4, and a plurality of roller wheels 5, also commonly known as idler wheels that guide, laterally align and support the track 3. The planetary drive system 4 and the plurality of roller wheels 5 are located at separate positions within the endless drive track system 2. For example, when the drive rollers 6 (see FIGS. 2 and 3) of the planetary drive system 4 rotate in a clockwise direction, the endless track 3 is driven in the clockwise direction. The roller wheels 5 also rotate in the clockwise direction due to the frictional engagement of the roller wheels 5 with the driven endless track 3. Alternatively, the roller wheels 5 can be positively driven. Consequently, the drive rollers 6, the roller wheels 5 and the endless track 3 rotate in a common direction.
The endless track 3 is comprised of a plurality of drive sections 7. FIG. 2 shows an exploded perspective view of an exemplary drive section 7 where the drive rollers 6 of the planetary drive system 4 engage the drive section 7 of the endless track. Each drive section 7 includes an interior surface 8 and an exterior surface 9. The exterior surface 9 of each drive section 7 faces away relative to the endless drive track system 2 and includes a tread that contacts the ground over which the tracked vehicle 1 travels. The interior surface 8 of each drive section 7 faces toward the endless drive track system 2 and includes a plurality of drive lugs 10 extending inwardly from the interior surface 8.
Typically, each drive lug 10 includes four faces 10a-10d. Faces 10b and 10d are drive faces that extend in a direction transverse to the traveling direction of the endless track 3 and are contacted and driven by the drive rollers 6. An arrow A indicates the traveling direction of the endless track 3 as being from right to left, although the traveling direction of the endless track 3 can also be from left to right. The remaining faces 10a and 10c are longitudinal faces and extend in a direction substantially parallel to the traveling direction of the endless track 3. At least one purpose of the longitudinal faces 10a and 10c is to guide the endless track 3 as it travels past the roller wheels 5.
FIG. 3 shows a schematic diagram of the drive rollers 6 rotated in a clockwise direction by the planetary drive system 4 to engage and drive the drive lugs 10. When a drive section 7 of the endless track 3 reaches the planetary drive system 4, the rotated drive rollers 6 of the planetary drive system 4 contact drive face 10b of the drive lugs 10 to drive the endless track 3 in the clockwise direction. Similarly, when the drive rollers 6 are rotated in the counterclockwise direction, the drive rollers 6 contact drive face 10d of the drive lugs 10 to drive the endless track 3 in a counterclockwise direction. As such, upon contacting the drive face 10b or 10d of the drive lugs 10, the drive rollers 6 are able to drive the drive section 7 of the endless track 3 in the desired traveling direction. The drive rollers 6 repeat the above-described operation for every drive lug 10 passing through the planetary drive system 4.
As the drive rollers 6 of the planetary drive system 4 are typically constructed from wear-resistant materials, e.g., metals, and the endless track 3 is typically made of a polymeric material, the engagement of the drive rollers 6 with the drive lugs 10 of the endless track 3 may result in the wearing down or erosion of the drive lugs 10. Although the drive rollers 6 are illustrated as substantially filling the region between adjacent drive lugs 10, the size of the drive rollers 6 can be made smaller, as long as the drive rollers 6 are capable of engaging the drive faces 10b and 10d of the drive lugs 10.
FIG. 4 shows an exploded perspective view where the roller wheels 5 engage a drive 7 section of the endless track 3 driven in the clockwise, i.e., right to left, direction. In the illustration, three roller wheels 5 are provided on a common shaft, although more or less than three rollers can be provided, and independent shafts may be desirable, depending on need. As such, because of the frictional engagement of the endless track 3 with the roller wheels 5, each roller wheel 5 is rotated in the clockwise direction with the drive section 7 of the endless track 3. The rotation of the roller wheels 5 provides even support across the endless track 3 in an orthogonal direction relative to the direction the track 3 is driven.
FIG. 5 is cross-sectional view of the roller wheels 5 engaging the drive section 7 of the endless track 3 shown in FIG. 4, as taken along section line 5--5. The spacing of the roller wheels 5 relative to the drive lugs 10 is such that the roller wheels 5 should not contact the longitudinal faces 10a and 10c of the drive lugs 10 while engaging the drive section 7. To this end, the total length of the combined distances X and Y is typically about 3/8"-1/2".
As represented by the bi-directional arrows in FIG. 5, the endless track 3 has a tendency to move with respect to the roller wheels 5 in the direction parallel to the axes of the roller wheels 5. Consequently, the roller wheels 5 may contact the longitudinal faces 10a and 10c of the drive lugs 10. As the roller wheels 5 are typically constructed from wear-resistant materials and the endless track 3 is typically made of a polymeric material, the frictional engagement of the roller wheels 5 with the drive lugs 10 results in the wearing down or eroding of the longitudinal faces 10a and 10c of the drive lug 10.
For example, as shown in FIG. 6, which is an enlargement of the dashed box of FIG. 5, contact between the roller wheels 5 and the longitudinal faces 10a and 10c of the drive lug 10 results in the wearing away of the longitudinal faces 10a and 10c. The worn away portions of the drive lug 10 are represented by the shaded region R. The gradual decrease in the surface area weakens the drive lugs 10 and causes early failure of the drive belt. For example, the endless drive belt may need to be replaced after 300 working hours due to erosion of the drive lugs. Also, due to the reduced surface area, "slipping" can occur between the drive rollers 6 of the planetary drive system 4 and the endless track 3.
Furthermore, the wearing away of the longitudinal faces 10a and 10c weakens the structural integrity of the endless track 3 and permits an increase in lateral "play", i.e., the extent the endless track 3 moves in the direction parallel to the axes of the roller wheels 5. Also, the wearing away of the endless track 3 frequently requires that the endless track 3 be replaced, which requires a stoppage of work, increases the cost associated with using the tracked vehicle 1, and increases labor costs.